Since thrombopoietin is a polypeptide cytokine consisting of 332 amino acids and it promotes platelet production by stimulating differentiation and proliferation of a megakaryocyte via a receptor, it is expected as an agent for morbidity of a blood disease accompanied with abnormality of the platelet number such as thrombocytopenia. A nucleotide sequence of a gene encoding a thrombopoietin receptor is described in Non-Patent Document 1. In Patent Document 1 and Patent Document 2, low-molecular peptides having affinity for the thrombopoietin receptor are also known, but oral administration of these peptide derivatives are not generally practical.
As a low-molecular compound having affinity for the thrombopoietin receptor, a 1,4-benzothiazepine derivative is described in Patent Document 3 and Patent Document 4, a 1-azonaphthalene derivative is described in Patent Document 5, and a 1,3-thiazole derivative is described in Patent Document 6 to 22.
[Patent Document 1]
Japanese Patent Application Laid-Open (JP-A) No. 10-72492
[Patent Document 2]
International Publication WO 96/40750
[Patent Document 3]
JP-A No. 11-1477
[Patent Document 4]
JP-A No. 11-152276
[Patent Document 5]
International Publication WO 00/35446
[Patent Document 6]
JP-A No. 10-287634
[Patent Document 7]
International Publication WO 01/07423
[Patent Document 8]
International Publication WO 01/53267
[Patent Document 9]
International Publication WO 02/059099
[Patent Document 10]
International Publication WO 02/059100
[Patent Document 11]
International Publication WO 02/059100
[Patent Document 12]
International Publication WO 02/062775
[Patent Document 13]
International Publication WO 2003/062233
[Patent Document 14]
International Publication WO 2004/029049
[Patent Document 15]
International Publication WO 2005/007651
[Patent Document 16]
International Publication WO 2005/014561
[Patent Document 17]
JP-A No. 2005-47905
[Patent Document 18]
JP-A No. 2006-219480
[Patent Document 19]
JP-A No. 2006-219481
[Patent Document 20]
International Publication WO 2007/004038
[Patent Document 21]
International Publication WO 2007/036709
[Patent Document 22]
International Publication WO 2007/054783
[Non-Patent Document 1]
Proc. Natl. Acad. Sci. USA, 1992, vol. 89, p. 5640-5644